squid and authentication with openldap

hello all, i am running squid 2 on a SuSe 6.3 and it works OK. Now I want to restrict my users' access logged on a Windows NT terminal server. So I cannot restrict them by IP numbers because there is only one. Now I have seen the parameter "authenticat_program" for an external authenticator. In squid.conf they tell about the program ncsa_auth, but Suse seems to use LDAP access. I started LDAP server and tried to enter a user, but I was not successful. I read the administrator guide from openldap.org but I think I need more basic understanding in this subject. Is there any easy introduction to administration of openldap, adding users, defining access rights... Thanks for any hint Richard Hegewald